# define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int findnumber(int arr1[], int sz)
{
	int result = 0;
	for (int i = 0; i < sz; i++)
	{
		result ^= arr1[i];
	}
	return result;
}


int main()
{
	int arr1[] = { 1,2,3,4,5,1,2,3,4 };
	int sz = sizeof(arr1) / sizeof(arr1[0]);
	int result = findnumber(arr1, sz);
	printf("%d\n", result);
	return 0;
}